Citing the growing enthusiasm over the protected bicycle lanes on Kinzie Street, city officials announced plans Monday for a second cycle-friendly thoroughfare.

The protected bike lanes on Kinzie, both eastbound and westbound between Milwaukee Avenue and Wells Street, were largely completed early this month.

But the city formally opened the bike lanes Monday, while also unveiling plans for a similar stretch on Jackson Boulevard between Damen Avenue and Halsted Street.

The bike lanes on Kinzie initially caused some confusion and grumbling among motorists, even as they made the street more attractive to cyclists. Bike traffic at Kinzie and Clinton streets was up 60 percent from May, according to a city survey.

Cyclists are buffered from traffic along the half-mile stretch by plastic posts and a car parking lane. The project cost about $140,000.

On a July weekday with good weather, there were 656 bicyclists on Kinzie, compared with 413 on a comparable day in May before the lanes opened, said Chicago Department of Transportation spokesman Brian Steele.

Another city survey found that bicycles accounted for about 48 percent of the morning rush-hour traffic on southbound Milwaukee at Kinzie.

“We are delighted” with the city’s efforts, said Melody Geraci, deputy director of the nonprofit Active Transportation Alliance, involved in efforts to make streets safer for bicyclists, pedestrians and motorists in the Chicago region.

Still, Geraci acknowledged that for many people, the changed streetscape is likely to be a “shock to the system.”

“There (will be) some confusion, and change is tough,” Geraci said. “We really do have to do our job to explain (the changes) to the public.”

The Kinzie lanes are the first in Mayor Rahm Emanuel’s proposal to install 25 miles of protected bike lanes each year. Other big cities, including New York, Washington and Portland, Ore., have similar lanes.

The Jackson location was chosen for its width, bike traffic and connections to existing bike lanes and routes, city officials said

Work on the Jackson lanes, to be coordinated with a resurfacing project, is set to begin by early August.